Formation and Luminescent Properties of Al2O3:SiOC Nanocomposites on the Base of Alumina Nanoparticles Modified by Phenyltrimethoxysilane.

Al2O3:SiOC nanocomposites were synthesized by thermal treatment of fumed alumina nanoparticles modified by phenyltrimethoxysilane. The effect of annealing temperature in inert ambient on structure and photoluminescence of modified alumina powder was studied by IR spectroscopy as well as photoluminescence spectroscopy with ultraviolet and X-ray excitation. It is demonstrated that increase of annealing temperature results in formation of silica precipitates on the surface of alumina particles that is accompanied by development and spectral evolution of visible photoluminescence. These observations are discussed in terms of structural transformation of the surface of Al2O3 particles.

Natural Minerals Coated by Biopolymer Chitosan: Synthesis, Physicochemical, and Adsorption Properties.

Natural minerals are widely used in treatment technologies as mineral fertilizer, food additive in animal husbandry, and cosmetics because they combine valuable ion-exchanging and adsorption properties together with unique physicochemical and medical properties. Saponite (saponite clay) of the Ukrainian Podillya refers to the class of bentonites, a subclass of layered magnesium silicate montmorillonite. Clinoptilolits are aluminosilicates with carcase structure. In our work, we have coated biopolymer chitosan on the surfaces of natural minerals of Ukrainian origin - Podilsky saponite and Sokyrnitsky clinoptilolite. Chitosan mineral composites have been obtained by crosslinking of adsorbed biopolymer on saponite and clinoptilolite surface with glutaraldehyde. The obtained composites have been characterized by the physicochemical methods such as thermogravimetric/differential thermal analyses (DTA, DTG, TG), differential scanning calorimetry, mass analysis, nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy to determine possible interactions between the silica and chitosan molecule. The adsorption of microquantities of cations Cu(II), Zn(II), Fe(III), Cd(II), and Pb(II) by the obtained composites and the initial natural minerals has been studied from aqueous solutions. The sorption capacities and kinetic adsorption characteristics of the adsorbents were estimated. It was found that the obtained results have shown that the ability of chitosan to coordinate heavy metal ions Zn(II), Cu(II), Cd(II), and Fe(III) is less or equal to the ability to retain ions of these metals in the pores of minerals without forming chemical bonds.

Complex investigations of structural and thermal properties of silica-titania adsorbents.

Mesoporous titanium-containing silicas with different Titania contents were investigated. The structural parameters of the materials were characterized by low-temperature adsorption/desorption of nitrogen and X-ray diffraction analysis. The thermodesorption of water using the quasi-isothermal thermogravimetry as well as the differential scanning calorimetry were used to characterize thermal and surface properties of these materials. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent/water interfaces were calculated. It was stated that the increase of Titania content causes a gradual decrease of specific surface area and formation of biporous structure inside the tested materials. The water thermodesorption from the surface proceeds in two or three stages, which is connected mainly with pore distribution and TiO2 content. One can observe the increase of the total surface free energy (ΔGΣ) with the increasing TiO2 content, but the largest ΔGΣ value at the adsorbent/strongly bound water interface is exhibited by the adsorbent of intermediate content (30%) of TiO2. Freezing temperature of water contained in the pores of the studied materials is connected largely with their porous structure. Due to the well developed porous structure, the water freezing process is a multi-stage one.

[Properties of papain, immobilized on organosilica]. / Svoistva papaina, immobilizovannogo na organokremnezeme.

Papain, a proteolytic enzyme, is used in the reactions of organic synthesis for preparing peptides. The use of immobilized papain with this aim is very promising. Preparations of papain immobilized by organosilica have been studied for their physicochemical properties as well kinetics of the papain immobilization by amino-organosilica activated by cyanuric chloride. Retention of the enzyme activity of immobilized papain reached 40% and depended on the amount of enzyme bound with the carrier. Kmobs of the immobilized enzyme did not differ significantly from that of the soluble enzyme. After immobilization the pH-optimum an pH-profile of the catalytical activity of papain remained unchangeable. For the period of 20 days immobilized papain has lost 20-50% activity.

[The effect of potassium ferricyanide and copper (II) ions on the properties of immobilized galactose oxidase]. / Vliianie ferritsianida kaliia i ionov medi (II) na svoistva immobilizovannoi galaktozooksodazy.

Preparations of galactosooxidase (EC 1.1.3.9) immobilized by activated aminorganosilica have been used to study potassium ferricyanide and bivalent copper ions on the enzyme activity and stability in continuous reactor under pulse conditions. Introduction of potassium ferricyanide is shown to activate the enzyme and inconsiderably affecting its stability with the substrate absent and inducing inactivation of galactosooxidase in the process of catalytic reaction. Cu2+ ions, exerting no effect on the activity of immobilized galactosooxidase, evoke the enzyme inactivation in the process of catalysis.

[Immobilization of urease from Staphylococcal saprophyticus L-1 on activated silica]. / Immobilizatsiia ureazy is Staphylococcus saprophyticus L-1 na aktivirovannykh kremnezemakh.

The paper deals with immobilization of urease obtained from Staphylococcus saprophyticus L-1 on the organic silica surfaces. The process completion time (4-5 h) and the optimal pH of binding (7-8) are practically independent of the chemical nature of the carrier surface. The value of the specific activity of urease grafted to silica depends not only on the type of the enzyme-carrier bond, but also on the macromolecule protein-to-silica distance. The extent of the retained enzyme activity is shown to be 26% after sorption on the initial silica. It grows to 100% with an increase of the organic radical length which separates the biocatalyst and the carrier.

[Inactivation of o-diphenoloxidase in the pyrocatechol oxidation reaction]. / Inaktivatsiia o-difenoloksidazy v protsesse reaktsii okisleniia pirokatekhina.

The inactivation kinetics of o-diphenoloxidase isolated from potato tubers was studied in the process of pyrocatechol oxidation. The enzyme when saturated with the substrate is inactivated with the inactivation rate constant kin = 0.5-1.0 min-1; kin depends on the initial concentration of pyrocatechol. The ultimate yield of the enzymic reaction product increases linearly with the initial concentration of the enzyme. Introduction of ethylene-diaminosulphate, a substance which condenses with o-quinones, does not increase the operation stability of o-diphenoloxidase. The data obtained evidence for inactivation of o-diphenoloxidase either at the level of the enzyme-substrate complex or due to bimolecular reaction with the substrate.

[Various properties of galactose oxidase from Fusarium graminearum IMV-F-1060 immobilized on aminoorganosilochromes]. / Nekotorye svoistva galaktozooksidazy iz Fusarium graminearum IMB-F-No. 1060, immobilizovannoi na aminoorganosilokhromakh.

Galactose oxidase preparations are obtained from Fusarium graminearum IMV-F-N 1060 immobilized on aminoorganosilochromes activated by cyanuron chloride and 2.4-toluylene diizocyanate. The immobilized preparations were studied for their selective action on different carbohydrate substrates and for the pH-medium dependence of the obtained preparation activity. Potassium ferricyanide is established to have an activating effect on the immobilized enzyme. It is shown that the immobilized galactose oxidase preparations may be used for the analysis of galactose and lactose.

[A method for determining theo-diphenoloxidase activity in the pyrocatechol oxidation reaction]. / Metod opredeleniia aktivnosti o-difenoloksidazy v reaktsii okisleniia pirokatekhina.

A new simple and sensitive spectrophotometric method is suggested for determining the catecholase activity of diphenoloxidase. The method is based on the enzymatic oxidation of pyrocatechol to 1,2-benzoquinone (BQ) in the presence of the excess of ethylenediamine sulphate (EDA). The condensation product (products) of BQ and EDA (P365) is stable in the solution and possesses strong absorption in the range of 365 nm. The molar absorption factor, E365 (under condition that the molar reaction ratio of catechol to P365 is 1:1) is 15500 M-1 cm-1 on the average. Optimal reaction conditions (pH 7.0, T=25-30 degrees C, [EDA]o = 5 mg/ml) are determined. The advantages and restrictions of the suggested technique in comparison with the methods described earlier are discussed.

[Properties of urease immobilized on silochrome by means of disulfide bonds]. / Svoistva ureazy, immobilizovannoi na silokhrome s pomoshch'iu disul'fidnykh sviazei.

Grafting of SH-groups to the silica surface through the hydrolytically stable Si-C-bond is conducted by gamma-mercaptopropyltrimethoxysilane. After 2,2'-dithiobis-p-nitrobenzoic acid (Ellman's reagent) activation of sulphydryl groups urease of microbial origin was immobilized by these carriers. Certain properties of the preparations obtained were studied. The Km of the enzyme during nonporous silicon aerosil immobilization is shown to remain without considerable changes. The found variations in properties of silochrome-immobilized urease are caused by the diffusion inhibition for the substrate and product of the reaction observed even when the substrate concentration is two orders higher than Km.

[Kinetics of the immobilization of trypsin on activated silichrome]. / Kinetika immobilizatsii tripsina na aktivirovannom silokhrome.

Trypsin is studied for kinetics of its immobilization on the surface of a porous spheric inorganic carrier with the grafted aldehyde groups in the surface layer. This process is found to be controlled by the enzyme diffusion. It is shown possible to use a body of mathematics known for kinetics of physical adsorption on the porous adsorbents to describe kinetics of protein chemosorption on the analogous carriers. A simple method is suggested for plotting a kinetic curve of the enzyme immobilization on the matrix with any sizes of particles from the experimentally obtained kinetic curve of its binding on the carrier with a definite diameter of particles.

[Properties of urease immobilized on the functional organic silica surface]. / Svoistva ureazy, immobilizovannoi na poverkhnosti funktsional'nykh organokremnezemov.

The paper deals with kinetics of the urea hydrolysis by microbial-origin urease dissolved and immobilized on the organic silica surface. It is shown that hydrolysis kinetics for soluble urease is described by the Michaelis-Menten equation until the concentration of urea reaches 1 M. Two fractions differing in the Michaelis constant are revealed for silochrome immobilized urease. The rate of urea hydrolysis by native and immobilized urease was studied depending on the pH value in presence of the substrate in the 1 M and 5 mM concentration. The hydrolysis rate of 1 M urea in the buffer-free solution by silochrome-immobilized urease is practically independent of pH within 4.5-6.5. Application of a 2.5 mM phosphate-citrate buffer as a solvent causes an increase in the hydrolysis rate within this pH range. For a soluble urease the 1 M urea hydrolysis rate dependence on pH is ordinary at pH 5.8-6.0. If the substrate concentration is 5 mM, the pH-dependences for the rate of the urea hydrolysis by silochrome- and aerosil-immobilized urease are close and at pH above 6.0 coincide with those for a soluble enzyme. The found differences in the properties of soluble and immobilized ureases are explained by the substrate and reaction products diffusion.

[Stability of Penicillium vitale immobilized catalase in continuous decomposition of hydrogen peroxide]. / Issledovanie stabil'nosti immobilizovannoi katalazy Penicillium vitale pri dlitel'nom razlozhenii perekisi vodoroda.

The process of hydrogen peroxide continuous decomposition by the preparation of the fungus Penicillium vitale catalase immobilized by aminoorganosilica which were activated by glutaric aldehyde, cyanuric chloride or 2,4-toluylene diisocyanate. Catalase with an oxidized carbohydrate component was used as well. Such a modified enzyme was directly bound with the surface of aminocontaining silica and alumina. It is shown that in the process of H2O2 decomposition the preparations of immobilized catalase are inactivated. The decrease in its activity is described by a model which suggests that rates of hydrogen peroxide decomposition and enzyme inactivation are described by the first order equations. A method for calculation and prediction of mean time of continuous operation of columns with bound catalase and other immobilized enzymes is suggested in terms of the given model.

[Immobilization of Penicillium vitale Pidopl. et Bilai catalase by inorganic carriers]. / Immobilizatsiia katalazy Penicillium vitale Pidopl. et Balai na neorganicheskikh nositeliakh.

An efficient method is developed for P. vitale catalase immobilization through the oxidized carbohydrate enzyme component, using silochrome. The method provides the enzyme binding without losing its catalytic capacity in the immobilized preparation. When the enzyme is immobilized by high-dispersed silica containing isocyanate, aldehyde groups or active atoms of chlorine, 8, 15, and 20 mg of the enzyme is bounded per 1 g of the carrier, respectively, its catalytic capacity being completely retained. A dependence is established for the degree of catalase bonding and catalytic capacity of the immobilized enzyme of the enzyme carrier ratio in immobilization. The catalytic activity of the immobilized catalase preparations reaches 2 000 Becker units/l g. The preparations are stable in storage. Some of their properties are studied.

[Pronase E and P immobilization on aminoorganosilica surface]. / Immobilizatsiia pronazy e i p na poverkhnosti aminoorganokremiezema.

Immobilization of pronase E and P was performed on sylochrome modified by gamma-aminopropyltrietoxysilane using cyanuric chloride, 2,4--toluylenediisocyanate, glutaric aldehyde and also on sylochrome by means of titanium tetrachloride. The esterase and caséinolytic activities of the immobilized preparations and their stability during storage were determined. The increased thermostability of the immobilized preparation is established. The influence of the enzyme: carrier ratio on the immobilization process and activity of the enzymes was studied. It is shown that application of glutaric aldehyde favours the best retention of the esterase activity (73%), whereas the caseinolytic activity is better retained (31%) when titanium tetrachloride was used.

[Catalytic properties of immobilized cells of methane-oxidizing bacteria]. / Kataliticheskie svoistva immobilizovannykh kletok metanokisliaiuschchikh bakterii.

The article deals with conditions for immobilization of methane-oxidizing bacteria cells as well as with catalytic properties of the immobilized cells. The method of immobilization in polyacrylamide gel is shown to be not suitable for cells of methane-oxidizing bacteria. The greatest number of cells (85%) is immobilized on sylochrome modified by cyanuric chloride. However, the catalytic properties of the methane-oxidizing bacteria are better retained when the bacteria are immobilized on sylochrome modified by isocyanate. A stand installation is created for studying the catalytic properties of the immobilized cells oxidizing substrates in the gas phase.

[Trypsin immobilization on organo-silica surface]. / Immobilizatsiia tripsina na poverkhnosti organokremnezemov.

The methods are suggested for immobilizing trypsin on the organo-silica surface by means of cyanuric chloride and maleic anhydride. The analysis of kinetics of the enzyme carrier coupling shows that at 22 degrees C the immobilization time on the surface of organo-silicas activated with cyanuric chloride and maleic anhydride is 70 and 35 min, respectively. The immobilized trypsin is shown to be more thermostable as compared to the soluble one. The half-life of the immobilized trypsin at 55 degrees C is about 40 h.

[Plasma prekallikrein activation by highly dispersed organic silica]. / Aktyvatsiia prekalikreïnu plazmy krovi vysokodyspersnymy orhanichnymy kremnezemamy

Human and animal blood plasm precallikrein was studied as activated by the high-dispersed preparations of silica (aerosils) which carry on their surface various chemically grafted organic radicals. It is shown that hydrophilic silica containing -COOH, -HN2, -OH groups, contrary to the hydrophobic ones, are efficient in activating human plasm precallikrein. Precallikrein activation is dependent on concentration of hydrophilic aerosil, temperature and specific surface of the activator.